The present invention relates to a system for and a method of controlling torque distribution for a pair of primary driving wheels and a pair of secondary driving wheels of a motor vehicle of the four wheel drive type, and more particularly to a system for and a method of actively controlling such torque distribution.
JP No. 61-157437 discloses a system for controlling a torque distribution ratio of a portion of torque delivered toward secondary front driving wheels to the remaining portion of torque delivered to primary rear driving wheels. According to this system, the torque distribution ratio is varied in response to a revolution speed differential between the front wheel side and rear wheel side.
This known system increases the torque distribution ratio to increase the torque portion delivered to the front wheels in response to an increase in revolution speed differential induced when the vehicle travels on a road with low friction coefficient. If, under this four-wheel drive condition, the driver turns the steering wheel to change the direction of heading of the front wheels to cause the vehicle to make a turn, the vehicle exibits an understeer characteristic, and thus the readiness of the vehicle to change its heading is poor.
An object of the present invention is to eliminate the above mentioned drawback encountered in the known torque distribution control system.
More specifically, an object of the present invention is to improve a system for and a method of controlling torque distribution over wheels of a motor vehicle such that, when the vehicle is making a turn, the readiness of the vehicle to turn its heading is improved without decreasing the torque portion delivered to the front wheels.